Your Paintbrush Might Need A Comb
A paintbrush can look clean on the outside while still holding a surprising amount of paint deep between its bristles. That's especially true if you've been working with thicker paint or haven't cleaned the brush immediately after using it. Simply rinsing the outside may not be enough to get everything out.
Before you give up on a brush or spend money replacing it, try reaching for something you probably already have: a comb. After cleaning the brush as thoroughly as you can, gently run the teeth of a comb through the bristles. Start near the base and work toward the tips, allowing the comb to pull out paint that's trapped deeper inside. You may be surprised by how much comes loose.
This little trick can help separate clumped bristles and remove leftover paint that ordinary rinsing misses. Keeping your brushes properly cleaned also helps them stay in better shape for your next project. Just use a little care. You don't want to aggressively bend or tear the bristles. It's a simple step, but if you've ever ruined a perfectly good brush because paint dried inside it, you'll probably wish you'd known about this one sooner.